Chemical sensors for both gases and liquid phase gain an increasing importance for the control of chemical processes and environmental issues, for medical purposes and the like. There is a wide variety of chemical sensors available on the market. The chemical sensor devices can be roughly separated as working on the basis of one of two major principles: the first is that electrochemical characteristics are affected by the adsorption of the analyte onto or into a sensitive layer or by combustion of the analyte. According to the second principle, changes in the optical properties are induced by the presence of an analyte. Both changes can be measured by respective detectors.
With respect to sensors working according to the second principle, where also the inventive sensor can be assigned to, sensor arrays are known, where the fluorescence and the optical absorption properties of organic dyes are used for chemical sensing. Such a sensor is for example disclosed in a paper of John J. Lavigne et al. “Solution-Based Analysis of Multiple Analytes by a Aensor Array: Toward the Development of an Electronic Tongue”, in Journal of American Chemical Society 1998, 120, 6429–6430. The described sensor allows for the simultaneous identification of multiple analytes in solution. Poly-(ethylene glycol)-poly styrene (PEG-PS) resin beads are positioned in a 3×3 array of wells formed in a Si/SiN-wafer. Signal transduction is accomplished by analysis of the absorption properties of the beads using a CCD-camera, interfaced with the sensor array. The use of CCD-cameras and optical fibers in sensor arrangements is also explained in a paper of P. Pantano and David R. Walt “Analytical Applications of Optical Imaging Fibers” in Analytical Chemistry 1995, 481 A ff.
But, the properties of the chemical sensors according to the state of art using organic dyes have numerous disadvantages: The number of selective indicator dyes for the reversible detection of analyte molecules or ions is limited. Therefore, a broadband application in sensor arrangement is not easily achievable. Further, the organic dyes do not show a stability desired for most chemical sensor arrangements.
It is further known that fluorescence properties of a semiconductor bulk material can be changed and influenced by adsorbing chemicals at a surface. But, the utilisation of semiconductor bulk material as a chemical sensor only shows an insufficient change of optical properties upon exposure to an analyte to be detected.